In the patent application Ser. No. 08/073,045, now U.S. Pat. No. 5,384,678 filed on the same day as this application and entitled "A control and self-monitoring system, in particular for a multipole electrical apparatus such as a high tension circuit breaker", the Applicant describes a system in which each pole of the apparatus is associated with a microprocessor, the various microprocessors being connected to a serial bus under the control of a management member. (The disclosure of this copending application is expressly incorporated herein by reference.) The bus has other subscribers, such as members for measuring or checking various elements of the apparatus, such as the pressure of insulating gas or of oil used for hydraulic control.
In such a structure, in order to make it possible for the subscribers to perform their various action and monitoring tasks, each subscriber requires all or part of the information acquired or generated by the entire set of subscribers, and this applies in real time with synchronization that is as perfect as possible. This guarantees that at any given instant, the information shared between the subscribers does indeed have the same value for all of the subscribers. This constraint indicates that the local network must be capable of managing effectively and quickly a database which is distributed between the subscriber stations.
Remarkably, this concept is achieved by the FIP local network enabling a large number of stations to be interconnected. However, that local network has a very rich range of functions (e.g. bulletin board functions) thus requiring the frames that are interchanged to be relatively large in size, which has the drawback of giving rise to transmission efficiency that is too low for the applications envisaged in the present patent application. Furthermore, it requires a prior configuration operation to be performed on the software in each station when the network is switched on (tawing its power from an auxiliary voltage, in particular for the purpose of designating the data that the station is to produce or to consume. Together, these constraints make the FIP network ill-suited to the application envisaged by the Applicant, since relatively high refresh rates are required for a small number of data items, and the system must be capable of restarting quickly without supervision in the event of failures of the auxiliary power supplies or of the local network.
In any event, the number of subscribers on the bus is less than 8.